FIELD OF THE INVENTION
This invention relates to a color filter, manufactured by coloring a number of filter elements on a substrate, partitioned by a light-shielding portion of a predetermined pattern formed on the substrate, a display device using the color filter, an apparatus comprising the display device, an ink-jet head, and a method and apparatus for manufacturing the color filter.
With recent advances in personal computers, especially portable personal computers, the demand for liquid crystal displays tends to rise, especially color liquid crystal displays. However, in order to further popularize the use of liquid crystal displays, a reduction in cost must be achieved. Especially, it is required to reduce the cost of a color filter which occupies a large proportion of the total cost. Various methods have been tried to satisfy the required characteristics of color filters while meeting the above requirements. However, a method capable of satisfying all the requirements has not been established. The current methods will be described below.
The first method is a coloring method, which is the most popular method. In the coloring method, a water-soluble polymer material as a colorable material is coated on a glass substrate, and the coating is patterned into a desired shape by a photolithography process. The obtained pattern is dipped in a color bath to obtain a colored pattern. This process is repeated three times to form R, G, and B color filter layers.
The second method is a pigment dispersion method, which is currently replacing the coloring method. In this method, a pigment-dispersed photosensitive resin layer is formed on a substrate and patterned into a single-color pattern. This process is repeated three times to obtain R, G and B color filter layers.
The third method is an electrodeposition method. In this method, a transparent electrode is patterned on a substrate, and the resultant structure is dipped in an electrodeposition coating fluid containing a pigment, a resin, an electrolyte, and the like to be colored in the first color by electrodeposition. This process is repeated three times to form R, G and B color filter layers. Finally, these layers are calcined.
The fourth method is a printing method of dispersing a pigment in a thermosetting resin, performing a print operation three times to form R, G and B coatings separately, and thermosetting the resins, thereby forming colored layers. In the above methods, a protective layer is generally formed on the colored layers.
The point common to these methods is that the same process must be repeated three times to obtain layers colored in three colors, i.e., R, G and B. This results in an increase in cost. In addition, as the number of processes increases, the yield decreases. In the electrodeposition method, limitations are imposed on pattern shapes which can be formed. For this reason, with the existing techniques, this method cannot be applied to TFTs (thin film transistors). In the print method, a pattern with a fine pitch cannot be formed because of poor resolution and unevenness.
In order to eliminate these drawbacks, methods of manufacturing color filters by ink-jet systems are disclosed in Japanese Patent Laid-Open Nos. 59-75205, 63-235901, 1-217302 and 4-123005.
In the above manufacturing methods by the conventional ink-jet systems, an ink-jet head is scanned on a substrate to color a number of filter elements. However, these methods have a problem in that positions of filter elements are slightly shifted from coloring dot positions of the ink-jet head, because in these methods, change of intervals between the filter elements and change of arrangement of the filter elements, due to temperature change and temperature distribution of substrate, are not considered. This causes white omissions and other problems in the filter elements.